How To Open ADO Connection and Recordset Objects
Symptoms
ActiveX Data Objects (ADO) offers several ways to open both the Connection and Recordset objects. This article presents sample code for several common techniques for each object.
Resolution
There are several ways to open a Connection Object within ADO:
By Setting the ConnectionString property to a valid Connect string and then calling the Open() method. This connection string is provider- dependent.By passing a valid Connect string to the first argument of the Open() method.By passing a valid Command object into the first argument of a Recordset’s Open method.By passing the ODBC Data source name and optionally user-id and password to the Connection Object’s Open() method. There are three ways to open a Recordset Object within ADO:
By opening the Recordset off the Connection.Execute() method.By opening the Recordset off the Command.Execute() method.By opening the Recordset object without a Connection or Command object, and passing an valid Connect string to the second argument of the Recordset.Open() method. This code assumes that Nwind.mdb is installed with Visual Basic, and is located in the C:\Program Files\DevStudio\VB directory:
Option ExplicitPrivate Sub cmdOpen_Click()Dim Conn1 As New adodb.ConnectionDim Cmd1 As New adodb.CommandDim Errs1 As ErrorsDim Rs1 As New adodb.RecordsetDim i As IntegerDim AccessConnect As String’ Error Handling VariablesDim errLoop As ErrorDim strTmp As StringAccessConnect = “Driver={Microsoft Access Driver (*.mdb)};” & _”Dbq=nwind.mdb;” & _”DefaultDir=C:\program files\devstudio\vb;” & _”Uid=Admin;Pwd=;”‘—————————’ Connection Object Methods’—————————On Error GoTo AdoError’ Full Error Handling which traverses’ Connection object’ Connection Open method #1:Open via ConnectionString PropertyConn1.ConnectionString = AccessConnectConn1.OpenConn1.CloseConn1.ConnectionString = “”‘ Connection Open method #2:Open(“[ODBC Connect String]“,”",”")Conn1.Open AccessConnectConn1.Close’ Connection Open method #3:Open(“DSN”,”Uid”,”Pwd”)Conn1.Open “Driver={Microsoft Access Driver (*.mdb)};” & _”DBQ=nwind.mdb;” & _”DefaultDir=C:\program files\devstudio\vb;” & _”Uid=Admin;Pwd=;”Conn1.Close’————————–’ Recordset Object Methods’————————–’ Don‘t assume that we have a connection object.On Error GoTo AdoErrorLite’ Recordset Open Method #1:Open via Connection.Execute(…)Conn1.Open AccessConnectSet Rs1 = Conn1.Execute(“SELECT * FROM Employees”)Rs1.CloseConn1.Close’ Recordset Open Method #2:Open via Command.Execute(…)Conn1.ConnectionString = AccessConnectConn1.OpenCmd1.ActiveConnection = Conn1Cmd1.CommandText = “SELECT * FROM Employees”Set Rs1 = Cmd1.ExecuteRs1.CloseConn1.CloseConn1.ConnectionString = “”‘ Recordset Open Method #3:Open via Command.Execute(…)Conn1.ConnectionString = AccessConnectConn1.OpenCmd1.ActiveConnection = Conn1Cmd1.CommandText = “SELECT * FROM Employees”Rs1.Open Cmd1Rs1.CloseConn1.CloseConn1.ConnectionString = “”‘ Recordset Open Method #4:Open w/o Connection & w/Connect StringRs1.Open “SELECT * FROM Employees”, AccessConnect, adOpenForwardOnlyRs1.CloseDone:Set Rs1 = NothingSet Cmd1 = NothingSet Conn1 = NothingExit SubAdoError:i = 1On Error Resume Next’ Enumerate Errors collection and display properties of’ each Error object (if Errors Collection is filled out)Set Errs1 = Conn1.ErrorsFor Each errLoop In Errs1With errLoopstrTmp = strTmp & vbCrLf & “ADO Error # ” & i & “:”strTmp = strTmp & vbCrLf & “ADO Error# ” & .NumberstrTmp = strTmp & vbCrLf & “Description” & .DescriptionstrTmp = strTmp & vbCrLf & “Source” & .Sourcei = i + 1End WithNextAdoErrorLite:’ Get VB Error Object’s informationstrTmp = strTmp & vbCrLf & “VB Error # ” & Str(Err.Number)strTmp = strTmp & vbCrLf & “Generated by ” & Err.SourcestrTmp = strTmp & vbCrLf & “Description” & Err.DescriptionMsgBox strTmp’ Clean up gracefully without risking infinite loop in error handlerOn Error GoTo 0GoTo DoneEnd Sub
ERROR NOTES Only the ADO Connection object has an errors collection. The observant reader will notice that a lightweight error handler is in effect for the RecordSet.Open examples. In the event of an error opening a RecordSet object, ADO should return the most explicit error from the OLEDB provider. Some common errors that can be encountered with the preceding code follow.
If you omit (or there is an error in) the DefaultDir parameter in the connect string, you may receive the following error:
ADO Error # -2147467259
Description [Microsoft][ODBC Microsoft Access 97 Driver] ‘(unknown)’
isn’t a valid path. Make sure that the path name is
spelled correctly and that you are connected to the server
on which the file resides.
Source Microsoft OLE DB Provider for ODBC Drivers
If there is an error in the Dbq parameter in the connect string, you may receive the following error:
ADO Error # -2147467259 Description [Microsoft][ODBC Microsoft Access 97 Driver] Couldn’t find
file ‘(unknown)’.
Source Microsoft OLE DB Provider for ODBC Drivers
The preceding errors also populate the Connection.Errors collection with the following errors:
ADO Error # -2147467259
Description [Microsoft][ODBC Driver Manager] Driver’s
SQLSetConnectAttr failed
Source Microsoft OLE DB Provider for ODBC Drivers
ADO Error # -2147467259
Description Login Failed
Source Microsoft OLE DB Provider for ODBC Drivers Note that for each error, the ADO Error number is the same, in this case translating to 0×80004005, which is the generic E_FAIL error message. The underlying Component did not have a specific error number for the condition encountered, but useful information was never-the-less raised to ADO.